Separation of plutonium from uranium and fission products by adsorption



I 2,819,144 SEPARATION OF PLUTONIUM FROM URANIUM AND FISSION PRGDUCTS BY ABSORPTION Glenn T. Seaborg and John E. Willard, Chicago, 11]., as-

signors to the United States of America as represented by the United States Atomic Energy Commission No Drawing. Application May 18, 1943 Serial No. 487,428 12 Claims. (Cl. 2314.5)

The invention relates to methods of separating materials and more particularly relates to the separation of fission products and/or uranium from each other and from element 94 by adsorption methods.

An object of the invention is to provide means for obtaining element 94 from neutron irradiated uranium in more concentrated form than there present.

Another object of the invention is to provide means for separating dangerous and harmful products from useful products in a neutron irradiated uranium. mass.

A further object is to provide a mass containing element 94 which is particularly adapted for use as a source of atomic power.

Another object is to provide a mass containing element 94 which is. substantially pure element 94.

Another object is to provide fission products of value for military purposes.

Other objects and advantages of this invention will become apparent as the following detailed description progresses.

In this specification and claims the name of the element, unless otherwise indicated, designates generically the element either in its free or combined state. The designation element 94 is used throughout this specification and claims to describe the elementhaving an atomic number of 94. Element 94 is also referred to in this specification and will probably become known in the art as plutonium, symbol Pu. Pu or Pu means the isotope of element 94 having a mass number of 239. Likewise element 93 means an element of atomic number of 93. Element 93 is also referred to as neptunium, symbol Np.

The fission products referred to in this specification are the large number of elements of lesser atomic number than uranium produced from the bombardment of uranium with neutrons. The reaction of neutrons with U results in a break down of its heavy nucleus into two fragments which undergo beta particle disintegration into chains of two groups. The reaction of slow neutrons with U may be exemplified as follows:

Two groups of elements are formed, a light group with atomic numbers from 3544-and a heavy group with atomic numbers from 51-58. The fission products with which We are particularly concerned arethose having a half life of more than three days since they remain in the reaction mass in substantial quantities at least one month after reaction. These products are chiefly Sr Y (57 day halfilife), Zr, Cb, and Ru of the group of atomic numbers from 3544; and Te Te I Xe Cs (many years half life), Ba (12 day half, life), La and Ce of 20 day and. 200 day half lives from the group of atomic numbers from 51-58 incl.

In addition to the fission products in the'neutron irradiated uranium mass there are also present transuranic elements resulting from the reaction of neutrons of thermal or resonance energies with U This reaction is:

2,819,144 Patented Jan. ,7, 1 958 The reaction ispreferably carriedout withneutrons of below the fast neutron stage, i. c. with neutrons ofresonance or thermal energies. Since element 94 itself reacts with slow or fast neutrons the reaction of the uranium withthe neutrons is terminated before all ofthe'94 is converted to fission productsand preferably Whilea substantial amount of uranium remains in the mass.

The neutron irradiated uranium mass therefore contains element 94, element 93, fission products, uranium, and minor amounts of other elements such as UX and UX The fission products, according to a particular object of this invention, are to be separated from the mixture with the 94, because they are toxic and deleteriously affect the utilization of the 94 as a source of power.

The uranium may also be removed to increase the concentration of 94 and this also maybe done by the process of our invention.

The neptunium decays to plutonium with a half life of 2.3 days so that its separation from the plutoniumis not so important.

The reaction of uranium with neutronsmay be carried out at such a slow rate of introduction of neutrons that a large proportion of the 93 decays to 94 during the reaction, or the mass may be stored for several days after the reaction to obtain more 94, or the 93 and94 may be separated together and the mixture stored before use so as to decrease the proportion of 93 and increase that of the 94. p I

We have discovered that diatomaceous earth has the property of adsorbing high proportions. of. element '94 from a solution of element 94, uranium, and fission products while adsorbing only small proportions of ura nium and fission products.

Our experiments have shown that when a solution of 10% UO (NO -6H O containing month-old fission products and tracer amounts of plutonium is passed through a column of diatomaceous earth (of 93% SiQ content), over 95% of the plutonium is adsorbed and only about5% of the uranium is adsorbed from the first portion to pass through the column. Less than 10% of the beta-emitting and only about 25% of the gamma-emitting fission products are adsorbed. Other evidence indicates that a similar efliciency is obtained withrnacro amounts of plutonium nitrate, in which theplutonium is in a valcnt state of not greater than +4, as for example +3 or +4.

Silica gel, colloidal aluminum oxide, fullers earth, adsorbent charcoal, and magnesium silicates (trisilicate and sesquisilicate) have also been tried. These materials showed a preferential adsorption for plutonium ion over uranyl ion for tracer amounts of plutonium in 10% uranyl nitrate solutions. The magnesium silicates and alumina shown a preferential adsorption for plutonium over ura' nium about as good as diatomaceous earth. Silica gel also has a high preferential adsorption. We regard these materials as operable in our process of separating macro amounts of plutonium from solutions containing plutonium, uranium, and fission products. For this purpose, however, diatomaceous earth is a highly eificient adsorbent for obtaining a concentrated mass of plutonium from solutions of neutron irradiated uranium. I

It is to be understood that any diatomaceous earth or colloidal form of SiO is suitable.

We have found that the adsorption of plutonium on diatornaecous earth is high in the pH range of 3.7 to 2.3 but falls off rapidly at pH below 2 so that itis' of little value at below a pH of 1. The adsorption is also very low-from (NH CO solution at pH 9.3. The adsorption is preferably carried out at a pH of from'about 2.0 [090.

The efiiciency of adsorption of plutonium on diatomaceous earth falls off rapidly with increasing concentrat tion of UO (NO .6H O (pH maintained at 2.0 or

higher), particularly at concentrations greater than 30%. The adsorbed plutonuim may be quantitatively eluted from the column of diatomaceous earth with nitric acid, suitably 6 N HNO The following examples are given to illustrate the invention.

EXAMPLES 50 cc. of a 10% solution of uranium nitrate hexahydrate containing 94 tracer (50-year 94) was introduced into the top of a 1 cm. diameter column packed with 6 g. (15.5 cm.) of diatomaceous earth having an Slo -content of 93%. The solution was allowed to flow by gravity, un til it reached the bottom of the column. A gentle suction was then applied and successive portions of the solution were collected. The volume of each portion and the time required for its collection were recorded. Aliquots of each portion were analyzed for 94 and uranium and the percentage of each of these elements which had been removed from the solution in its passage through the column was determined. The amount of 94 removed varied from 100% to 94%, with perhaps a slight downward trend with successive portions of the solution which passed through the column. The amount of uranium found to be removed varied from to 3%, with an average over the 50 cc. of about 7%.

After the fifth sample had been collected, the level of the uranyl nitrate solution in the column had just been sucked down to the top of the packing. 6 N HNO was then added to to the top of the column and the suction was continued. The sixth portion of liquid collected contained 5.5 cc. of the original uranyl nitrate solution (the hold-up in the column) plus the first 5.5 cc. of the acid wash. This portion contained 97% of the total 94 which was present in the 50 cc. of uranyl nitrate solution initially added. The results are tabulated below.

Table 1.Adsorption of 94 and uranium on the diatomaceous earth column Percent of Sample Minutes Volume, Percent of Percent of adsorbed N o. of flow cc. 94 ad- U ad- 94 removed sorbed sorbed by acid Repeated use of the same column. In order to determine whether the 6 N HNO wash aflects the ability of the diatomaceous earth to adsorb 94, the column for which data are given in Table l was washed with HNO of a pH of 2.5 (the approximate pH of 10% in the pH range of 3.7 to 2.3 (the natural pH of the 10% solutions discussed in part A above is 2.3), but starts to fall off in the range between 2.3 and 1.6. This adsorbing ability was found to be less than 1% at a pH of 1 and is likewise low in (NH CO solution at a pH of -9. In order to obtain the results which are given in Table 2 the pH of 10% UO (NO .6H O solutions was adjusted;

. 4 to different values in the acid range by addition of nitric acid or sodium hydroxide, and the solutions were shaken with the diatomaceous earth which was added in the proportion of l g. per 10 cc. of solution.

Table 2.-Eflect of pH on adsorption of 94 on diatomaceous earth Percent of p sorbed 1.6- 2.3 3.27- 3.;5 88 NiiliiiQfIIII "6 Effect of UO (NO .6H O concentration on the ad sorption of 94 by diatomaceous earth. In the practical extraction of 94 from uranium, it is desirable to keep the volume of solution small and therefore the concentration of uranyl nitrate high for convenience and speed in handling. Results obtained by shaking 1 gm. of diatomaceous earth having a SiO -content of 93% with 10 cc. of UO (NO .6H O solution (concentrations varying from 10% to 60%) indicate that the adsorption ability for 94 falls olf sharply at the higher concentrations (Table 3). The pH of these solutions was adjusted with sodium hydroxide, except as otherwise indicated.

Table 3.Adsorpti0n 0 94 on the diatomaceous earth at difierent concentrations of UO (NO .6H O

Natural pH of UO (NO .6H O solutions.-Since the adsorption of 94 from uranyl nitrate solutions by the diatomaceous earth varies with the pH of the solutions, a semi-quantitative determination of the variation of this pH with UO (NO .6H O concentration has been made. It was found that the pH of the more concentrated solutions was low enough to prevent adsorption of 94 on this substance. A second series of determinations was then made in which ammonium acetate was added to uranyl nitrate solutions of different concentrations to raise the pH until a permanent precipitate appeared, in order. to learn the maximum pH that might be used at each concentration. The results are shown in Table 4. In one experiment at 60% UO (NO .6H O concen acetate, ammonium hydroxide or sodium hydroxide was used.

Table 4.pH 0f UO (NO .6H O solutions pH at pH of which ppt.

Concentration of solution original appeared solution with The pH of these concentrated uranyl nitrate solutions was rather lower than we had-expected. In order to 2&1 9,144

test whether ornot this=was due"to*= some "free acidin I the I crystals introduced; in the manufacturing "process, some uranylnitrate (Merck reagent quality) was recrystallized 'twiceandthe'pH of -the solution measured. No significant change was found.

' Efiectof diatomaceous earthcolumns on the pH of uranyl nitrate slutions.lt has been repeatedly observed that whenuranylnitrate solutions arepassedthrough a column 'packed' with the" diatomaceous .earth containing 93% SiO which has not-previously been used, the pH of the first-portion ofithe solutiontocome through is higher than when itwas introduced into the column. Theseobservations have been made on uranyl nitrate solutions inthe pH range 1.6 to 2.8. The volumes'of the initial effluent testedhave been roughly equal to the volume of'the diatomaceousearth packing in the column, and the observed pH increase has been 0.3 to 0.4 of a pH unit. Later portions of solution passing through the column do not have their pH changed. It is--important to be aware of this limited neutralizing ability of I the diatomaceous earth in order to avoid effects due to pH change when one isstudying the efiectof other variables on adsorption by diatomaceous earth.

.Eflect of HNO concentration on elution of adsorbed 94 from diatomaceous earth.When 94 is adsorbed on.

the diatomaceous earth columns, it may be quantitatively eluted with 6 N HNO In order to determine whether more dilute solutions of acid mightbe used, columns 1 containing adsorbed-94 have. been washed .with '20 cc.

:of HNO -solutions of different concentrations' The time of passage of 20cc. was in each case about one hour. The results given in Table 5 indicate that solutions 2 N and less in 'HNO are not as effective inremoving adsorbed 94 from diatomaceous earth as is the 6 N acid.

Included in the table are similar data obtained with distilled water, which are of interest in considering whether the smallamount of uranium which isadsorbed with 94 from uranyl nitrate solutions can be washed from the column without washing ofi the 94. It seems probable that this can be done.

Table 5.-Elution of adsorbed 94 from the diatomaceous earth column Adsorption of 94 from 30% and 40% solution of UO (NO .6H O by diatomaceous earth c0lumns.It has been shown that the efficiency of adsorption of 94 from uranyl. nitrate solutions by shaking with diatomaceous earth decreases with increasing uranyl nitrate concentration and with decreasing pH. Experiments have been conducted to determine whether more satisfactory adsorption could be obtained from solutions of UO (NO .6H O of concentrations as high as 30% or 40% (normal pH 1.5 to 1.7) by passing them through columns of diatomaceous earth rather than by shaking with the adsorbent. A column 47 mm. in diameter containing one pound of diatomaceous earth having an SiO content of 93% was used in two experiments with 40% UO (NO .6H O containing tracer quantities of 94. In the first experiment, in which the solution was introduced at its natural pH -1.6, the first 300 cc. of efiluent (pH 2.0) had a 94 content 74% lower than the input liquid, while four subsequent fractions of the efiluent totaling 2000 cc. showed an average 94 content only 13% lower than the input liquid. In the second experiment, with a "freshpaclcing of the column, the pH of the'input solu- ""tion was' raised to 2.25 by addition of sodium hydroxide.

-. 95 of: the 94 Wasfoundto havebeen adsorbed from the first=600 cc.' 'of efiluent, while an average of55% was adsorbed from three subsequent portions, totaling 2000 cc. These results indicate that 94 cannot be satisfactorily adsorbed from 40% UO (NO .6H O solutions at-pH 2.25 or below. It has been pointed out earlier that satisfactoryadsorption does occur from 10% solutions at pH as low as 2.3. Satisfactory adsorption of 94 from 40% solutions may be attained at'pH higher than 2.3. However, the practical ditficulties-in r'edissolving the precipitate which is always formed in the processes of raising the pH of concentrated uranyl nitrate may be greater than the inconvenience of using the large volumes required by 10% solutions.

Data showing that 30% UO (NO .6H O at its nor mal pH of -1.7 can actually elute 94 from diatomaceous earth columns are shown in Table 6. These data are taken from an experiment in which cc. of a 30% so1ution of UOg(NO .611 0 containing 94 was added to a 1 cm. diameter column which had been filled with diatomaceous earth containing 93% SiO by sucking it in as a slurry. When the tracer solution had all entered the diatomaceous earth, a 30% UO (NO .6H O solu- Table 6.-Elution of adsorbed 94 from diatomaceous earth column by 30% UO (NO .6H O

Percent of Sample V0l., cc. pH 94 washed through Efiect of deuteron bombardment of diatomaceous earth 011 its ability to adsorb 94.A 0.4 g. sample of diatomaceous earth containing 93% Si0 which had been bombarded with a 20 ,ua. beam (-3000 curies) of deuterons from a cyclotron for 5 minutes was shaken with 4 cc. of 10% UO (NO .6H O containing 94 tracer. After centrifuging out the adsorbent, analysis of the supernatant liquid showed that 70% of its original 94 content had been adsorbed by the diatomaccous earth. Several similar determinations with the diatomaceous earth which had not been bombarded have resulted in adsorption of of the 94.

Separation of 94 from fission products by diatomaceous earth column-In order to determine whether diatornaceous earth would be effective in separating 94 from the fission products, the following experiment was conducted. 3 g. of (UO (NO .6H O which had been bombarded by the neutrons from 50,000 uahrs. of 12 m. e. v. deuterons on beryllium) was dissolved in 7 cc. of Water and allowed to flow, with the aid of suction, into a 1 cm. diameter column containing 12 g. of diatornaccous earth containing 93% SiO When this solution had all passed into the diatomaceous earth packing, 20 cc. of 30% U0 (NO .6H O solution was added to wash it through. Previous to the experiment, the pH of each of the above solutions had been adjusted to 2.7 with sodium hydroxide. A 0.180 cc. portion of the first liquid which came through the column was evaporated on a platinum dish and the betaand gamma-radioactivity was compared with that of an identical aliquot of the original solution which'had not passed through the column. The activity of the'effiuent sample (28 dis. per min), measuredwith an electroscope without absorber, was 80% of the activity of the liquid which had not passed through the column. When the two samples were shielded with 2 g./cm. of lead and the activities compared by means of a Geiger counter, the effluent sample again showed 80% (500 counts per minute) of the activity of the original material.

It has previously been shown that under the conditions of the above experiment, 95% of the tracer amounts of 94 present in the solution which passed through the column would be adsorbed. It may therefore be tentatively concluded that a diatomaceous earth adsorption column is able to separate 95% of 94 from at least 80% of uranium fission products (two weeks old) as well as from about 95% of the uranium in a uranyl nitrate solution of suitable concentration and pH.

The above experiment was done about two weeks after the bombardment of the uranyl nitrate. With increasing time after bombardment the percentage of the gammaactivity adsorbed by the diatomaceous earth columns increased and that of the beta-activity decreased due to the decay of some of the shorter lived fission product species. This fact is illustrated by experiments which showed that about 50% of the gamma-activity and of the beta-activity are adsorbed from solutions of neutron-bombarded uranyl nitrate at 30 days after bombardment.

Analysis of input and output liquids of solutions of neutron-bombarded uranyl nitrate which had been passed through the diatomaceous earth columns showed that a high percentage of the columbium in the solution, lesser amounts of the zirconium and minor amounts of other fission species were adsorbed while the adsorption of barium and lanthanum was very low.

The adsorption process by itself therefore provides a highly eificient separation of element 94 from uranium, and the fission products barium and lanthanum. It also provides a method of separating and isolating the fission products columbium and zirconium from the other fission products since those products are adsorbed in the diatomaceous earth to a much greater extent than the other fission products. a

The columbium and zirconium may be separated from the 94 in various ways. One method is to precipitate the 94 in its lower oxidation state (Pu+ with fluoride ion. The columbium and zirconium remain in solution.

The adsorbed 94 may also be further concentrated by treating it with a saturated solution of (NH CO The 94 is eluted leaving behind on the adsorption medium some species of fission products. Thus a further concentration of 94 is attained.

It will be understood that the above experiments were carried out on tracer quantities of 94.

Two types of experiment indicate that diatomaceous earth in addition to adsorbing high percentages of tracer quantities of 94 from small volumes of solution is also capable of adsorbing high percentages at relatively high concentrations from large volumes of solution.

The first type of experiment has involved the attainment of concentrations of 94 as high as 6 10- grams/ liter by concentrating the limited amounts of 94 at present available in very small volumes of 10% UO (NO .6H O solution (1 to .01 cc.). It has been found that diatomaceous earth (93% SiO added to such solutions in the ratio of 0.1 g. to 1 cc. of the solution is able to adsorb over 30% of the 94 over a concentration range from at least 10" to 10* grams/liter. This result indicates that, using columns packed with the diatomaceous earth, a high percentage removal of 94 from uranium-fission product mixtures may be attained at concentrations which will prevail in the large scale recovery of 94.

The second type of experiment has been designed to determine what volume of solution can be passed through columns packed with diatomaceous earth before the efficiency of adsorption drops below a useful value.

Using a 1.8 cm. diameter column packed with 36 g. of diatomaceous earth (93% SiO it has been found that the initial efficiency of adsorption of 94 which is nearly 100% gradually falls oif with continued passage through the column of 10% UO (NO .6I-I O. solution containing 94 tracer. However, the value does not reach zero until after the passage of three liters of solution and it maintains a value of over 80% until after the passage of about one liter of the solution. From this it follows, on the basis of calculations assuming a direct proportionality between adsorption capacity and weight of the diatomaceous earth, that a column containing 0.37 ton'of diatomaceous earth (4 ft. in diameter and 2.2 ft. high) is capable of adsorbing over 80% of the 94 from 1800 gal. of 10% UO (NO .6H O solution. The rates of flow through the diatomaceous earth columns are such that a 4 ft. diameter, 2.2 ft. high column would be expected to pass 470 gal. per eight hours. These facts indicate that columns of diatomaceous earth are capable of removing 94 from other products on a commercial scale.

Adsoprtion of plutonium by silica gel.-It has been found that silica gel shows an even greater capacity for plutonium adsorption than diatomaceous earth, and also it has been found that the plutonium can be readily and consistently eluted from the silica gel.

The preferred types of silica gels are those of low density such as about .8 g. per cc. but all types of silica gels are satisfactory.

Silica gel adsorption columns for the adsorption of plutonium should preferably be used at a pH as high as the normal pH (2.4) of 10% UO (NO .6H O solutions since the adsorption efliciency falls oil rapidly in the pH range from 2.5 to 1.5.

The recovery of adsorbed plutonium from the silica gel may be made readily and quantitatively by eluting with 6 N HNO The silica gel like the diatomaceous earth adsorbs zirconium and columbium fission species and these elements are not eluted with 6 N HNO Table 7 shows the adsorption of 18 and 'y fission activity from different aliquots of the eflluent solution during two cycles of running of a 40-60 mesh silica gel column.

1 Table 7.-Adsorption of 94 and fission products on column of 40-60 mesh Davison. silica gel [Wt of gel, 1200 g.; vol. of gel, -225D 00.; diam. of column, 9.5 cm.; height, 35 em.; direction of flow, upward; gel presoaked in water for 48 hours; experiments made with 10% UO2(NO3)2.6H O solutions -48 days after bombardment; total absorbed thickness for B measurements=6 ing/em]; total absorber thickness for 7 measurements, 2.5 g. of Pb/cmJ] FIRST CYCLE SECOND oYoLE After eluting U and 94 adsorbed in 1st cycle with 6 HNO and washing column with water until pH of emuent wash became 4.5, the column was reused for a fresh batch of irradiated uranyl nitrate with the following results:

Rate at which Percent of Percent of Volumes of efiluent collected, Percent oi F. P.'s 'y F. P.s fractions, cc. gzzlfijsfq. 94 adsorbed adsorbed adsorbed While there have been described certain embodiments of our invention, it is to be understood that it is capable of many modifications. Changes, therefore, may be made without departing from the spirit and scope of the invention as described in the appended claims, in which it is the intention to claim all novelty in the invention as broadly as possible.

We claim:

1. In the process of separating plutonium from fission products in a solution containing ions of a compound of plutonium in which the plutonium ions are in a valent state not greater than 1+4 and ions of compounds of fission products, the step of contacting the solution with an adsorbent selected from the group consisting of diatomaceous earth, silica gel, fullers earth, aluminum oxide, magnesium silicates and adsorbent carbon to selectively adsorb said plutonium ions from solution leaving ions of compounds of fission products in said solution, and then separating the adsorbent and adsorbed plutonium from the solution containing the ions of unadsorbed fission products.

2. In the process of separating plutonium from uranium in a solution containing ions of a compound of plutonium in which the plutonium ions are in a valent state not greater than j+4 and ions of a compound of uranium including uranyl ions, the step of contacting the solution with an adsorbent consisting of a diatomaceous earth, silica gel, fullers earth, aluminum oxide, magnesium silicates and adsorbent carbon to selectively adsorb said plutonium ions from solution leaving uranyl ions in said solution, and then separating the adsorbent and the adsorbed plutonium from the solution containing the uranyl ions.

3. In the process of separating plutonium from foreign products present in a solution of neutron irradiated uranium containing ions selected from the group consisting of plutonium ions in a valent state not greater than +4, ions of a compound of uranium, including uranyl ions, ions of compounds of fission products and mixtures of said ions, the step of contacting said solution with a siliceous adsorbent to selectively adsorb said plutonium ions from solution leaving ions of other product compounds in solution, and then separating the adsorbent and the adsorbed plutonium from solution containing ions of unadsorbed products.

4. The process of claim 3 wherein said siliceous adsorbent is diatomaceous earth.

5. The process of claim 3 wherein said siliceous adc sorbent is silica gel.

6. The process of obtaining plutonium in more concentrated state from neutron irradiated uranium containing plutonium and fission products which comprises forming a solution containing ions of the elements present in neutron irradiated uranium, regulating the pH to between 1 and 9, and contacting said solution with diatomaceous earth.

7. The process of separating plutonium from uranium which method comprises forming a solution containing ions of plutonium and uranium in which the concentration of uranium is not over about 30% and the pH is between 2 and 9, and contacting said solution with diatomaceous earth.

8. The process of separating plutonium from barium and lanthanum which comprises contacting a solution containing ions of said substances with diatomaceous earth to selectively adsorb plutonium and removing the adsorbent together with adsorbed plutonium from the solution.

9. The method of removing plutonium from a solution of neutron irradiated uranium containing ions of plutonium in a valent state not greater than +4 and ions of the elements present in neutron irradiated uranium which method comprises adsorbing said ions of plutonium on a siliceous adsorbent, and then dissolving the adsorbed plutonium with a selective solvent for the plutonium which is a nonsolvent for the adsorbent.

10. The step in the process of recovering plutonium by adsorption which consists of desorbing the adsorbed plutonium compound with an aqueous solution of ammonium carbonate.

11. A method of recovering plutonium from an aqueous solution which comprises contacting a solution containing plutonium in ionic state of a maximum valence of +4 with an adsorbent of the group consisting of diatomaceous earth, silica gel, fullers earth, aluminum oxide, magnesium silicates and adsorbent carbon for a time suflicient to permit adsorption of plutonium by the adsorbent and removing the adsorbent with adsorbed plutonium from the solution.

12. A process of separating plutonium values having a maximum oxidation state of +4 from values selected from the group consisting of uranium values, fission product values and mixtures of said values, said values being contained in an aqueous solution, comprising contacting said aqueous solution with an adsorbent selected from the group consisting of diatomaceous earth, silica gel, fullers earth, aluminum oxide, magnesium silicates and adsorbent carbon whereby said plutonium values are adsorbed while said other values remain in solution, and separating said plutonium-containing adsorbent from said solutions.

References Cited in the file of this patent UNITED STATES PATENTS 1,059,531 Ebler Apr. 22, 1913 1,142,153 Ebler June 8, 1915 1,934,838 Andrussow Nov. 14, 1933 2,129,733 Fulton et al Sept. 13, 1938 2,204,072 Dean June 11, 1940 OTHER REFERENCES Hackh: Chemical Dictionary, 2nd ed., pages 112, 734; P. Blakiston, Philadelphia (1931).

Seaborg: The Actinide Elements, p. 317 (1954), McGraw-Hill Book Co., New York.

UNITED STATES PATENT OFFICE Certificate of Correction 7 Patent No. 2,819,144. January 7, 195a Glenn T. Seaborg et a1.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below,

Column 1, line 50, for U read U column 8, line 52, for absorbed read absorber. 1

Signed and sealed this 3rd day of March 1959.

Attest: KARL H. AXLINE, ROBERT C. WATSON, Attesting Ofioer. domniaaiameof Patents.

UNITED STATES PATENT OFFICE Certificate of Correction Patent No. 2,819,14t January 7, 1958 Glenn T. Seaborg et 21.1.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below,

Column 1, line 50, for U read U column 8, line 52, for absorbed reed absorber.

Signed and sealed this 3rd day of March 1959.

Attract: KARL H. AXLINE, ROBERT C. WATSON, idtteatz'ng Ofioer. Oomniuimr of Patents. 

1. IN THE PROCESS OF SEPARATING PLUTONIUM FROM FISSION PRODUCTS IN A SOLUTION CONTAINING IONS OF A COMPOUND OF PLUTONIUM IN WHICH THE PLUTONIUM IONS ARE IN A VALENT STATE NOT GREATER THAN +4 AND IONS OF COMPOUNDS OF FISSION PRODUCTS, THE STEP OF CONTACTING THE SOLUTION WITH AN ADSORBENT SELECTED FROM THE GROUP CONSISTING OF DIATOMACEOUS EARTH, SILICA GEL, FULLER''S EARTH, ALUMINUM OXIDE, MAGNESIUM SILICATES, AND ADSORBENT CARBON TO SELECTIVELY ADSORB SAID PLUTONIUM IONS FROM SOLUTION LEAVING IONS OF COMPOUNDS OF FISSION PRODUCTS IN SAID SOLUTION, AND THEN SEPARATING THE ADSORBENT AND ADSORBED PLUTONIUM FROM THE SOLUTION CONTAINING THE IONS OF UNADSORBED FISSION PRODUCTS.
 10. THE STEP IN THE PROCESS OF RECOVERING PLUTONIUM BY ADSORPTION WHICH CONSISTS OF DESORBING THE ADSORBED PLUTONIUM COMPOUND WITH AN AQUEOUS SOLUTION OF AMMONIUM CARBONATE. 